An electric vehicle equipped with only an electric motor as driving source for travel outputs very quiet running sounds during low speed running. Further, a hybrid vehicle equipped with an electric motor and an internal-combustion engine as driving source for travel outputs very quiet running sounds during low speed running only with an electric motor as driving source. This may cause pedestrians etc. to fail to notice an approach of such vehicles.
There is proposed for such a low noise vehicle a vehicle approach notification apparatus which notifies nearby pedestrians etc. of the presence of the vehicle by generating a notice sound signal whose frequency changes depending on the vehicle speed and outputting a notice sound based on the generated notice sound signal towards an area external to the vehicle (e.g., refer to Patent Literature 1).
In addition, some notice sounds include pseudo engine sounds or pseudo running sounds that are generated as composite tones (chords) formed of several frequency components. Furthermore, to enable pedestrians etc. to recognize vehicle speeds, some notice sounds are processed such that the frequency of each frequency component constituting a notice sound is increased as the vehicle speed increases.